JP7443510B2 - Vapor cell for electromagnetic field imaging - Google Patents

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 62/941,572, filed November 27, 2019, entitled "Vapor Cells for Imaging of Electromagnetic Fields. " This application also claims priority to U.S. Application No. 16/996,652, filed August 18, 2020, entitled "Vapor Cells for Imaging of Electromagnetic Fields." The disclosures of these applications are incorporated herein by reference.

The following description relates to vapor cells for electromagnetic field imaging.

Over-the-air (OTA) testing is important for many systems that utilize electromagnetic radiation to obtain and communicate information (eg, radar systems, medical imaging systems, cellular systems, etc.). Furthermore, the design, manufacture, and testing of such systems during deployment is also important to ensure compliance with regulations. The difficulty of such testing increases as the electromagnetic frequencies utilized by systems scale to higher frequencies (e.g., above 30 GHz) and as the integration coupling between multiple components of the system becomes tighter. growing. An example of system integration of high frequency electronics is the fusion of antennas with transceiver systems and amplifiers. Testing of such highly integrated and sophisticated systems, especially in the mm-wave regime, is widely recognized as a looming problem for the automotive and transportation, radar, and telecommunications industries.

1 is a schematic diagram of an exemplary vapor cell having ribs or walls forming an internal support structure; FIG. 1B presents a top and partial side view of the example vapor cell of FIG. 1A; FIG. 1B is a schematic diagram of the example vapor cell of FIG. 1A in which one optical window includes a pocket formed therein; FIG. 1A is a schematic diagram of the example vapor cell of FIG. 1A including a pocket with two optical windows formed therein; FIG. 1B is a schematic diagram of the example vapor cell of FIG. 1A in which a portion of the frame serves as a first optical window and a second optical window joined to the frame includes a pocket formed therein; FIG. 2 is a schematic diagram of an example vapor cell having a dielectric 202 that includes multiple walls defining multiple square cells. FIG. 2B is an alternative implementation of the example vapor cell of FIG. 2A in which multiple walls define multiple hexagonal cells; FIG. 2B is a schematic diagram of the dielectric of the example vapor cell of FIG. 2B, with a portion of the dielectric serving as an optical window; FIG. 2 is a graph showing modeled reflection and transmission from 30 GHz to 50 GHz for an exemplary flat optical window. 2 is a graph showing modeled reflection and transmission from 30 GHz to 50 GHz of an exemplary patterned optical window. FIG. 2 is a schematic diagram of an example perimeter wall including a tapered structure projecting into an interior volume. 1 is a top view contour graph of an exemplary vapor cell having an optical window with decreasing effective dielectric constant; 5A is a contour graph of the example vapor cell of FIG. 5A corresponding to a side cross-sectional view perpendicular to the x-axis; FIG. 5B is a contour graph of the example vapor cell of FIG. 5A corresponding to a side cross-sectional view perpendicular to the y-axis; FIG. FIG. 5B is a schematic top view showing circular regions of different dielectric constants in the optical window of FIG. 5A; 5D is a schematic top view of an exemplary optical window having circular regions of differing dielectric constants as shown in FIG. 5D resulting from the arrangement of circular pockets as rotationally symmetric concentric rings; FIG. FIG. 2 is a schematic top view of an exemplary optical window having a terraced cross section that provides a tapering effective dielectric constant. 6B is a schematic side view of the example optical window of FIG. 6A; FIG.

In a general aspect, a vapor cell for imaging electromagnetic radiation is disclosed, including a method for manufacturing such a vapor cell. In some implementations, the vapor cell includes ribs that form an internal support structure and partition the internal volume of the vapor cell into multiple sub-volumes. The internal support structure may provide support for the optical window of the vapor cell. The plurality of sub-volumes may be identical in configuration (eg, shape, size, etc.) and may form a periodic array of sub-volumes. This manufacturing method may enable the fabrication of thin vapor cells that can be used to image electromagnetic fields using a Rydberg atomic electrometer. The phase resolution across the vapor cell is determined by its thickness compared to the wavelength of the target radiation field and by the spatial resolution of the optical field used to prepare the atoms in the vapor and read out their reactions.

In some implementations, the vapor cell can reflect an optical field or signal (e.g., a laser beam) that is used to create a suitable frame and then prepare the atoms in the vapor and read them out. It can be fabricated by bonding a thin dielectric mirror to a frame (eg, bonding a Bragg reflector to a frame). A first optical window can be bonded onto the frame. The first optical window may be a top optical window. Such bonding may include frit bonding, anodic bonding, cold contact bonding, or some other bonding method. Cold contact bonding may be used to seal the second optical window (eg, the bottom optical window) to the vapor cell to maintain the purity of the atomic or molecular sample. However, in some variations, other bonding methods (eg, frit bonding, anodic bonding, etc.) may be used. In some situations, cold contact bonding is advantageous over bonding methods that require high temperatures and/or high voltages. These latter methods result in significant outgassing, which can impair the performance of the vapor cell when pure samples of atoms are utilized, such as in the case of Rydberg atom-based electric field sensing.

In some variations, the frame includes a stem for introducing an atomic or molecular sample into the vapor cell after sealing the second optical window to the frame. For example, the shank may be a tubular extension formed of vitreous silica (or quartz glass) that can be fused and closed after introduction of the atomic or molecular sample. In some variations, the frame includes a fill hole for introducing vapor (eg, an atomic or molecular sample) into the vapor cell after sealing the second optical window to the frame. The fill hole may be cold sealed by contact bonding a cover or plug to the fill hole. However, other sealing methods may also be used.

In some implementations, the vapor cell includes a thin dielectric mirror (e.g., a laser beam) that can create a frame and then reflect an optical field or signal (e.g., a laser beam) used to prepare the atoms and read them out. For example, it can be fabricated by bonding an optical window with a Bragg reflector) to a frame. A first optical window can be bonded onto the frame. The first optical window may be a top optical window. The first optical window may include a dielectric mirror. Dielectric mirrors can be thin. Optionally, a dielectric mirror may be deposited on the surface of the first optical window. Also, in some cases, the dielectric mirror is attached to the surface of the first optical window (eg, via an adhesive or glue).

In some implementations, the vapor cell is configured such that the optical window is subatmospheric so that, for example, imaging the incident electromagnetic field at high spatial resolution may be possible by imaging light in different regions of the vapor cell. It has ribs along the frame to prevent it from warping. For example, crosstalk between different areas along the surface of the vapor cell can be minimized, thereby improving spatial resolution. In some implementations, a tapering refractive index is used along the edges of the vapor cell to prevent wall reflections from interfering with the measurements. The optical window can also be machined to reduce reflection of the high frequency electromagnetic field to be imaged. In some variations, the patterned wall can be machined to further reduce reflections from the wall, such as by attenuating the electric field amplitude. Still further, the ribs may be cut with small gaps so that the gas within the vapor cell, such as alkali atoms, can be evenly distributed throughout the vapor cell.

In some cases, vapor cells can be used for vapor cell magnetic measurements. In implementations where the sealing bond is performed near room temperature, an anti-spin relaxation coating can be applied to the vapor cell to increase the integration time of the vapor cell. Such vapor cells can be optically coupled through free space or by waveguides such as optical fiber bundles.

Accurate absolute measurements of high frequency electric fields (HFE) have been achieved by using Rydberg atoms in electrometers. There are several antenna measurement applications where this technology has significant potential to advance the prior art. However, challenges exist at certain ranges of antenna sizes (both large and small) and at high powers. These challenges can be alleviated by conductor-free HFE probes that are more electromagnetically transparent than anything in use today. The use of dielectric probes can lower the error floor that can be reached in these measurements, while providing a means to dramatically lower costs, thereby opening up new areas of application. Over the air (OTA) testing of high frequency electronic equipment is becoming increasingly important as these devices become more integrated, but testing them using traditional methods has become very difficult. By nearly completely removing undesirable materials from the probe, exceptionally high measurement accuracy can be achieved, which is important for the determination of electromagnetic fields radiated by a device under test (DUT).

The techniques presented herein enable the construction and operation of vapor cell electric field imaging devices such as those shown in FIGS. 1A-1E, such as CCDs for HFEs. Using atom-based electric field sensing, the resulting spatial and phase resolution allows both phase and amplitude to be imaged in a plane close to the DUT. The amplitude and phase information across the plane of the vapor cell sensor can be used to propagate the electric field to another location using well-known procedures such as Fresnel theory.

Accurate measurements of antenna radiation patterns are often required to validate the engineering science of antenna design and to ensure that antennas operate as intended in their given application. . Electromagnetic emissions from other types of devices are also important for testing, for example EMI from other HFE devices such as amplifiers. Prior art approaches to antenna pattern measurements utilize electric field probes, typically conductive antennas, where both the probe and antenna under test (AUT) are surrounded by a large anechoic chamber. These darkrooms are typically large sealed metal boxes coated on the inside with foam to absorb any radiation. To make even the most basic measurements, metal cables must be run between the AUT and the probe. Metallic structures in positioning devices further increase the complexity of the environment and are a source of error.

A more flexible Rydberg atom-based technology, such as the one presented herein, may make it easier to tailor the size of an anechoic chamber to individual applications and reduce the cost of chamber performance. For electrically compact antennas - those whose dimensions are small relative to their operating wavelength, the presence of excess metal structures ensures sufficient absorption of their radiation in all directions except the desired direction. This further exacerbates the difficult task of For power-only pattern measurements, Rydberg atomic electrometers do not require synchronization between the antenna and probe, allowing the AUT to be powered by a lightweight millimeter-scale oscillator, allowing the cable to be The need is completely eliminated.

In some implementations, the vapor cells presented in this disclosure provide multiple field point imaging devices for imaging the amplitude and phase of electromagnetic fields generated by high frequency electronic devices, such as antennas. imaging device). Such imaging devices can be lightweight and portable, allowing highly accurate calibration of antennas in the field or on the assembly line. Such features can be highly beneficial for many applications in communications, automotive radar, electronics, weather radar, and military radar. The vapor cell-based imaging device disclosed herein is suitable for imaging electromagnetic fields emanating from a DUT for over the air testing (OTA). OTA is desirable because it allows a non-invasive and non-destructive method to test a DUT. In some implementations, vapor cells enable one or more of the following advantages: [1] dielectric properties, [2] thinness (providing phase resolution), [3] structure. integrity, [4] large area for capturing the electromagnetic field, [5] uniformity of response, [6] reflective backing for imaging the optically readout field, [7] shank [8] use of tapering dielectric properties for impedance matching to reduce reflections from walls; [9] machining of windows to reduce reflections; [10] reflections. and [11] the ability to manufacture vapor cells of various sizes and frequencies of electromagnetic radiation on an industrial scale. Other advantages are possible. Incorporating these properties into a single vapor cell is highly advantageous and may enable its use for electric field imaging using atom-based electric field sensing.

Exemplary implementations of vapor cells are shown in FIGS. 1A-1E and 2A-2C. In particular, FIG. 1A shows a schematic diagram of an exemplary vapor cell with ribs (or walls) forming an internal support structure. FIG. 1B presents a top and partial side view of the exemplary vapor cell of FIG. 1A. This exemplary vapor cell includes a frame and two optical windows. The frame can be laser cut, etched, or machined (or any combination thereof) from silicon or glass. However, other materials (eg sapphire) may also be used. The frame includes ribbing or connecting walls that partition the internal volume into a plurality of sub-volumes or cells. The partial volumes may be uniform in size and shape and may be arranged according to a periodic array within the frame. Within the subvolume there is a vapor or gas (or a source thereof) for detecting target radiation. Laser cutting makes the manufacture of vapor cells more suitable for mass production. In many variations, an optical window on one side (bottom) of the vapor cell reflects one or more of the optical signals (or rays) used to initialize and read out atoms within the vapor cell. includes a multilayer Bragg reflector (or dielectric mirror) that is optimized for Bragg reflectors can be fabricated with alternating layers of _SiO2 and _TiO2 . However, other types of layers and their arrangements may be used. In some variations, the last layer of the Bragg reflector is formed of _SiO2 , allowing the Bragg reflector to be contact bonded to the frame.

If the Bragg reflector is made of another material rather than SiO ₂ , it is further possible to install a SiO ₂ adhesive layer on the surface of the Bragg reflector. The SiO ₂ adhesive layer may form or include a contact bondable surface. Other materials are also possible. For example, a TiO ₂ adhesive layer may be placed on the surface of the Bragg reflector. This layer may form or include a contact bondable surface. In some cases, the reflector needs to be dielectric and thin to reduce scattering of the incident field being measured. The top optical window can be attached to the frame using high temperature and/or high voltage capable bonding techniques, such as anodic bonding or glass frit bonding. If the frame is made of glass, a thin layer of Si can be deposited on the frame material as an adhesive layer for anodic bonding. It is also possible to contact bond the top layer and the frame if both are made of glass.

In some implementations, a pocket may be formed in one or both of the optical windows by laser machining or etching. FIG. 1C presents a schematic diagram of the exemplary vapor cell of FIG. 1A in which one optical window includes a pocket formed therein. FIG. 1D presents a schematic diagram of the exemplary vapor cell of FIG. 1A in which both optical windows include pockets formed therein. The pockets may be arranged to form a pattern. In some cases, the pockets may function to reduce the amount of material in the optical window while maintaining its structural integrity. In some cases, the pocket may function to define an effective dielectric constant that is different from the intrinsic dielectric constant associated with the material forming the optical window. This effective dielectric constant makes it possible to reduce the possibility that electromagnetic radiation (eg target radiation to be measured) will be reflected or scattered into the sub-volumes. However, other benefits are possible. In some of these implementations, one of the optical windows--eg, the bottom optical window--includes a mirrored surface. The mirrored surface can be on the inner surface or on the outer surface of the optical window. If the optical window includes a pocket, the pocket may define part or all of the outer surface.

In some implementations, the exemplary vapor cell includes an optical window that is integral with the frame, for example, one of the two optical windows shown in FIGS. 1A and 1B is integral with the frame. The optical window may be defined by the wall of the frame, which may have a flat outer surface. However, in some cases, the wall may include pockets along the outer surface. FIG. 1E presents a schematic diagram of the example vapor cell of FIG. 1A in which a portion of the frame serves as an optical window. This part may correspond to the wall of the frame and may have a mirrored surface on the inside. However, if the frame is made from a transparent material (eg glass), the mirrored portion may be on the outer surface. In these implementations, a second optical window that is not integral with the frame may be joined to the frame to confine vapor within multiple sub-volumes or cells. The second optical window may include a pocket formed therein.

The vapor cells disclosed herein may include a frame rib structure. The rib structure as shown in FIGS. 1A-1E and 2A-2C minimizes distortion of the optical window, e.g. due to atmospheric pressure, to enable imaging of the optical field across the plane of the vapor cell. It is selected as follows. The optical window is thin to reduce field under test (FUT) scattering. This configuration allows each light ray emanating from a region of the vapor cell to carry spatial information about the incident electromagnetic field (RF-mm), ie the FUT. Typically, the spatial resolution of the optical imaging will determine the spatial resolution of the incident electromagnetic field (FUT). Passages (eg, notches, channels, etc.) are cut into the ribs of the steam cell frame to allow gas or steam to uniformly fill the steam cell during manufacturing.

In some implementations, it may be possible to fill the vapor cell via a stem extending outwardly from the vapor cell (e.g., a stem extending outwardly from a side of the vapor cell). . The shank may represent a tubular structure that can be sealed, such as by melting, after filling the vapor cell. In some implementations, it may be optimal to fill the vapor cell through a small hole located on the side of the vapor cell in one of the optical windows or the frame. By contact bonding this small hole (or fill hole), the vapor cell can be sealed. In this case, larger windows can be sealed using high temperature and/or high voltage techniques. The fill hole need only be large enough to evacuate the internal structure and fill the vapor cell. In some variations, the fill hole need only be large enough to evacuate the vapor cell and pump it down to the desired pressure. This latter method includes a method for filling by chemical reaction, e.g. a getter source in the vapor cell, another chemical release mechanism, to fill the internal volume with the atomic or molecular species used in the measurement. Alternatively, a method by heat activation will be used when it can be carried out.

Referring now to FIG. 2A, a schematic diagram of an example vapor cell 200 having a dielectric 202 (or frame) that includes a plurality of walls 204 (or ribs) is provided. A plurality of walls 204 define square cells (or subvolumes) within dielectric 202 . However, the cells may have other shapes. For example, FIG. 2B presents an alternative implementation in which multiple walls 204 define hexagonal cells. Dielectric 202 also includes a first surface 206 and a second surface 208. A second surface 208 is disposed opposite the first surface 206 and the plurality of walls 204 extend from the first surface 206 to the second surface 208. In some cases, first surface 206 and second surface 208 are planar. In some cases, first surface 206 and second surface 208 are parallel to each other. The plurality of walls 204 includes a peripheral wall 210 and a plurality of interconnected walls 212. Peripheral wall 210 surrounds open volume 214 of dielectric 202 , and interconnected walls 212 are arranged within open volume 214 to partition open volume 214 into a plurality of cells 216 . Each of the cells 216 has a first opening 218 defined by the first surface 206 and a second opening 220 defined by the second surface 208. In some variations, as shown in FIGS. 2A-2B, the plurality of cells 216 form a periodic array (eg, a two-dimensional periodic array).

The example dielectric 202 may be formed of a material that is transparent to the electric field (or electromagnetic radiation) measured by the example vapor cell 200. The material may be an insulating material with a high resistivity, for example ρ>10 ³ Ω·cm, and may correspond to single crystal, polycrystalline ceramics or amorphous glass. For example, dielectric 202 may be formed of silicon. In another example, dielectric 202 may be formed of a glass containing silicon oxide (eg, SiO ₂ , SiO _x , etc.), such as fused silica glass, borosilicate glass, or aluminosilicate glass. In some cases, the material of dielectric 202 is, _for example, magnesium oxide (e.g. MgO), aluminum oxide (e.g. _Al2O3 ), silicon dioxide (e.g. _SiO2 ), titanium dioxide (e.g. _TiO2 ), zirconium dioxide, (e.g. oxide materials such as ZrO ₂ ), yttrium oxide (eg Y ₂ O ₃ ), and lanthanum oxide (eg La ₂ O ₃ ). The oxide material may be non-stoichiometric (eg, SiO _x ) or a combination of one or more binary oxides (eg, Y:ZrO ₂ , LaAlO ₃ , etc.). Also, in some cases, the material of dielectric 202 is a non-oxide material, such as silicon (Si), diamond (C), gallium nitride (GaN), calcium fluoride (CaF), and the like.

The exemplary vapor cell 200 has a first opening 218 having a surface 224 joined to a first surface 206 of the dielectric 202 to form a seal around each of the first openings 218. including a first optical window 222 that covers the. A second optical window 226 covers the second apertures 220 and is bonded to the second surface 208 of the dielectric 202 to form a seal around each of the second apertures 220. It further includes a surface 228. The first optical window 222 and the second optical window 226 can thus confine vapor (or a source of vapor) within the plurality of cells 216. In some variations, first optical window 222 includes a dielectric mirror, such as a Bragg reflector. A dielectric mirror may be disposed along a surface 224 of the first optical window 222 that is joined to the first surface 206 of the dielectric 202 . In some variations, second optical window 226 includes an anti-reflection coating.

The first optical window 222 and the second optical window 226 are made of a material that is transparent to electromagnetic radiation (e.g., laser light) used to probe the vapor sealed within the plurality of cells 216 of the dielectric 202. can be formed by For example, the material of the first optical window 222 and the second optical window 226 may be suitable for infrared wavelengths of electromagnetic radiation (e.g., 700-5000 nm), visible wavelengths of electromagnetic radiation (e.g., 400-700 nm), or ultraviolet wavelengths of electromagnetic radiation. (for example, 10 to 400 nm) can be transmitted. Furthermore, the material of the first optical window 222 and the second optical window 226 may be an insulating material with a high resistivity, for example ρ>10 ³ Ω·cm, such as single crystal, polycrystalline ceramics, or It can also correspond to amorphous glass. For example, the material of first optical window 222 and second optical window 226 may include silicon oxide (e.g., SiO ₂ , SiO _x , etc.), such as found in quartz, fused silica, or borosilicate glass. . In another example, the material of first optical window 222 and second optical window 226 is aluminum oxide (e.g., Al ₂ O ₃ , Al _x O _y , etc.), such as found in sapphire or aluminosilicate glass. ) may be included. In some cases, the material of the first optical window 222 and the second optical window 226 is, for example, magnesium oxide (e.g., MgO), aluminum oxide (e.g., Al ₂ O ₃ ), silicon dioxide (e.g., SiO ₂ ), titanium dioxide ( Oxide materials such as TiO ₂ ), zirconium dioxide (eg ZrO ₂ ), yttrium oxide (eg Y ₂ O ₃ ), lanthanum oxide (eg La ₂ O ₃ ), and the like. The oxide material may be non-stoichiometric (eg, SiO _x ) or a combination of one or more binary oxides (eg, Y:ZrO ₂ , LaAlO ₃ , etc.). Also, in some cases, the material of the first optical window 222 and the second optical window 226 is a non-oxide material, such as diamond (C) or calcium fluoride (CaF).

In some implementations, one of first optical window 222 and second optical window 226 is integral with dielectric 202. In these implementations, a portion of dielectric 202 acts as an optical window. For example, FIG. 2C presents a schematic diagram of the dielectric 202 of FIG. 2B in which a portion of the dielectric 202 serves as a second optical window 226. In FIG. 2C, a plurality of cells 216 extend from first surface 206 partially through dielectric 202. In FIG. First optical window 222 confines each cell 216 as it forms a seal around their corresponding first opening 218 . To fabricate dielectric 202 of FIG. 2C, a patterned layer may be applied to first surface 206 of dielectric 202 that includes holes that define the shape of a plurality of cells 216. The portion of first surface 206 exposed through the hole may then be contacted with a chemical etchant. Other manufacturing methods are possible.

The example steam cell 200 includes steam or a source of steam within each of the plurality of cells 216. The vapor may include components such as a gas of alkali metal atoms, a noble gas, a gas of diatomic halogen molecules, or a gas of organic molecules. For example, the vapor may include a gas of alkali metal atoms (eg, K, Rb, Cs, etc.), a noble gas (eg, He, Ne, Ar, Kr, etc.), or both. In other examples, the vapor may include a gas of diatomic halogen molecules (eg, F ₂ , Cl ₂ , Br ₂ , etc.), a noble gas, or both. In yet another example, the vapor may include a gas of organic molecules (eg, acetylene), a noble gas, or both. Other combinations of steam are possible, including other components. A source of steam may generate steam in response to an energy stimulus, such as heat, exposure to ultraviolet radiation, and the like. For example, the vapor may represent a gas of alkali metal atoms, and the source of vapor may represent an alkali metal atom gas that is sufficiently cooled to be in a solid or liquid phase when disposed within the plurality of cells 216. It can correspond to a collection of In some implementations, the source of steam is within one or more cells 216 defined by the plurality of walls 204, and the source of steam produces a gas of alkali metal atoms when heated. A liquid or solid source of alkali metal atoms (e.g., an azide compound containing alkali metal atoms) configured to.

In many implementations, the interconnected walls 212 include passageways (eg, channels or grooves) to allow vapor to flow between the plurality of cells 216. The passageways enable the example vapor cell 200 to maintain an even distribution of vapor across the plurality of cells 216 (e.g., equal pressure between cells 216, equal concentration of vapor within each cell 216, etc.) during operation. may become possible. This passageway may also allow multiple cells 216 to be filled with steam during manufacturing. Filling with vapor may be performed by introducing vapor through a fill hole in the dielectric 202, a fill hole in the first optical window 222, a fill hole in the second optical window 226, or some combination thereof. can. Such filling may also be accomplished by stimulating a source of steam disposed within one or more of the plurality of cells 216 with energy (eg, heat). In some variations, as shown in FIGS. 2A-2B, at least one of the interconnected walls 212 includes a passageway 230 that fluidly communicates cells separated by the at least one interconnected wall. include. In some variations, three or more of the interconnected walls 212 are joined at a union that includes passageways that provide fluid communication between cells adjacent to the union.

The interconnected walls 212 provide mechanical support for the first optical window 222 and the second optical window 226 while allowing the example vapor cell 200 to receive electromagnetic radiation over a large area. It may be a dimension (e.g., by thickness, width, diameter, etc.). In some variations, the interconnected walls 212 occupy 25 percent or less of the open volume 214 of the dielectric 202. In some variations, the interconnected walls 212 occupy 20 percent or less of the open volume 214 of the dielectric 202. In some variations, the interconnected walls 212 occupy 15 percent or less of the open volume 214 of the dielectric 202. In some variations, the interconnected walls 212 occupy 10 percent or less of the open volume 214 of the dielectric 202. In some variations, interconnected walls 212 occupy 5 percent or less of open volume 214 of dielectric 202. In some variations, the interconnected walls 212 occupy 3 percent or less of the open volume 214 of the dielectric 202.

In some implementations, dielectric 202 is thin such that each of the plurality of cells 216 forms a tubular cell. In these implementations, dielectric 202 has a height defined by the distance between first surface 206 and second surface 208 and a maximum dimension along a direction perpendicular to this height. It can have a defined width. In some variations, the height is less than or equal to 10 percent of the width. In some variations, the height is no more than 8 percent of the width. In some variations, the height is no more than 6 percent of the width. In some variations, the height is no more than 4 percent of the width. In some variations, the height is less than or equal to 2 percent of the width. In some variations, the height is one percent or less of the width. In some variations, the height is less than or equal to 0.5 percent of the width.

In some configurations, the example vapor cell 200 has one optical window without a dielectric mirror, such as the second optical window 226. The optical window can be provided with an antireflection coating for optical fields or signals (eg, light rays). Although the optical window can be coupled to the fiber array in some variations, free space coupling is advantageous to reduce interference and scattering from the FUT. As shown in FIG. 3B, first optical window 222 and second optical window 226 can be machined to reduce the amount of material but maintain structural integrity. Machining the windows to reduce the amount of material lowers their effective dielectric constant, resulting in a lower resistivity of the optical windows to the FUT. Machining thus reduces the effective refractive index of the optical window.

FIG. 3A presents graphs showing modeled reflection and transmission from 30 GHz to 50 GHz for an example flat optical window, and FIG. 3B presents graphs showing modeled reflection and transmission from 30 GHz to 50 GHz for an example patterned optical window. A graph showing the reflected reflection and transmission is presented. A patterned optical window is machined to have a well or pocket configuration on one surface. In some cases, the configuration of wells or pockets can be periodic. As shown by comparing the graphs of FIGS. 3A and 3B, the transmission of a patterned optical window is greater than that of a flat optical window. The reflection from a patterned optical window is lower than that from a flat optical window. Other methods of changing the effective dielectric constant may be used, such as altering the material with a laser to change the dielectric constant (eg, absorbing the laser's energy into the material).

2A-2B, one or both of the first optical window 222 and the second optical window 226 have an effective dielectric constant that is different from the intrinsic dielectric constant associated with the material forming the optical window. rate. In some implementations, one or both of first optical window 222 and second optical window 226 may include a first window surface opposite a second window surface. In these implementations, a first window surface (eg, surface 224 of first optical window 222) is bonded to dielectric 202. A plurality of pockets extend partially from the second window surface to the first window surface. The plurality of pockets may be configured to reduce the amount of material in the optical window while maintaining its structural integrity. In some cases, the plurality of pockets are sized such that the effective dielectric constant of the optical window is determined. This effective dielectric constant is different from the inherent dielectric constant associated with the material forming the optical window.

Reflections may also be reduced by configuring dielectric 202, first optical window 222, second optical window 226, or some combination thereof to taper toward peripheral wall 210. This taper may be achieved by machining during manufacturing and may allow for better impedance matching. Dielectric 202 also includes subwavelength structures machined into peripheral wall 210 to prevent reflection and excitation of walls 204 and to more uniformly react vapor within exemplary vapor cell 200 during operation. may have.

In some implementations, the example vapor cell 200 is configured to detect target radiation (eg, target radiation having a wavelength of at least 0.3 mm). For example, peripheral wall 210 includes a plurality of protrusions extending into open volume 214. The plurality of protrusions may function to impedance match electromagnetic radiation (eg, target radiation) propagating toward the surrounding wall 210. Such propagation may be parallel to one or both of first surface 206 and second surface 208, for example. Propagation may also occur within open volume 214 (or within multiple cells 216) of dielectric 202. In some variations, each of the plurality of protrusions has a largest dimension that is less than or equal to the wavelength of the target radiation. In some variations, the plurality of protrusions are evenly spaced along the peripheral wall 210. In some variations, each of the plurality of protrusions tapers into the open volume 214. For example, FIG. 4 presents a schematic illustration of an exemplary perimeter wall 400 that includes a tapered structure 402 projecting into an interior volume. The tapered structure 402 corresponds to a triangular protrusion with a base of 1 mm and a height of 3 mm, and serves to reduce electromagnetic reflection from the surrounding wall 400. Tapered structure 402 may be disposed along peripheral wall 400 such that the outer portion of the dielectric is symmetrical, for example symmetrical about an axis of rotation (eg, the z-axis in FIG. 4).

Referring now to FIGS. 5A-5C, contour graphs of an exemplary vapor cell having an optical window with decreasing effective dielectric constant are presented. The contour graph corresponds to a top view and two cross-sectional views of an exemplary vapor cell. A decreasing dielectric constant can be established using an optical window with circular regions of different dielectric constant (ε) as shown in FIG. 5D. In this configuration, the optical window may include several rotationally symmetric concentric annular pockets to reduce the effective dielectric constant. The pocket can be circular, as shown in Figure 5E. However, other shapes are possible. Still further, the pockets may have varying depths and may be distributed in a different pattern than that shown in FIG. 5E. Although three circular regions with different dielectric constants are depicted in FIG. 5D, the optical window may have other distributions of dielectric constant.

The contour graph shows the distribution of electric field strength in an exemplary vapor cell, quantified in units of volts per meter (V/m). The effective dielectric constant of each optical window is determined by three circular regions of different permittivity: the outer ring (ε=ε ₃ ), the inner ring (ε=ε ₂ ), and the center bounded by the inner ring. It gradually decreases due to the presence of a disk (ε=ε ₁ ). The distribution of electric field strength in the central disk is more uniform than in a vapor cell without tapering of dielectric constant in the optical window. The more uniform distribution is due to reduced reflections from the edges of the structure. The gradual decrease in dielectric constant establishes an effective dielectric constant that decreases in magnitude with increasing radial distance from the center of the vapor cell. Such a decreasing dielectric constant may reduce wall reflections of electromagnetic waves.

Other configurations of the optical window can provide effective dielectric constants that decrease in magnitude. For example, FIG. 6A provides a schematic top view of an exemplary optical window having a terraced cross section. FIG. 6B shows a side view of the example optical window of FIG. 6A. The terraced cross-section includes three steps to create an optical window thickness that increases as one moves a radial distance from the edge of the example optical window into its interior. In this example, the terraced configuration provides an effective dielectric constant that decreases in magnitude with increasing radial distance from the center of the example optical window. In this example, this effective dielectric constant can produce electric field strength distributions as shown in the contour graphs of FIGS. 5A to 5C.

Measurements of the power of the incoming electromagnetic field can be related to properties of the atoms via transition dipole moments and fundamental constants. In some cases, vapor cells as described herein can be used to measure electrical power with high precision within a controlled laboratory environment, with vapor cells providing self-calibrating absolute measurements of electric fields. It is possible. When measuring electromagnetic radiation from a DUT, the vapor cell can provide a self-calibrating absolute measurement of the power emitted by the DUT, which can be used in conjunction with a reference beam measurement to extract the phase of the electromagnetic radiation. can. The measurement may serve as a standard for each DUT. Still further, when a vapor cell is used in a holographic device with a reference beam, the device can make measurements that are completely self-calibrating, because the Rydberg atom-based power This is because by using the sensor (or vapor cell) as a reference, the reference wave power can be calibrated and stabilized. The geometry of the vapor cell can be determined to an accuracy of 10 μm or less by laser cutting the vapor cell frame or etching the vapor cell structure. OTA testing is required by many different parties, including telecommunications carriers, electronics manufacturers, and regulatory agencies. OTA testing may be associated with standards and can help ensure compliance with government regulations and avoid costly design errors. Compliance and testing can help the high frequency electronics industry meet demanding global market schedules and technical specifications.

In some implementations, a method of manufacturing a vapor cell includes obtaining a dielectric having a first surface and a second surface opposite the first surface. The method also includes removing material from the dielectric to form a plurality of walls extending from the first surface to the second surface. The plurality of walls includes a perimeter wall surrounding the open volume of the dielectric and interconnected walls disposed within the open volume to partition the open volume into a plurality of cells. Each of the plurality of cells has a first opening defined by a first surface and a second opening defined by a second surface. The method further includes bonding a surface of the optical window to the first surface of the dielectric to form a seal around each of the first openings. An optical window covers a first opening of the plurality of cells.

In some implementations, the optical window is a first optical window. In these implementations, the method includes disposing a steam or a source of steam within each of the plurality of cells. The method also includes bonding a surface of the second optical window to a second surface of the dielectric to form a seal around each of the second openings. A second optical window covers the second opening of the plurality of cells to confine the vapor or source of vapor within each of the plurality of cells.

In some implementations, removing material from the dielectric includes focusing a laser beam onto the dielectric to machine the material. In some implementations, removing material from the dielectric includes exposing the dielectric to a chemical to etch the material therefrom. In some implementations, removing material from the dielectric includes forming a passageway through at least one interconnected wall. The passageway is configured to allow cells separated by at least one interconnected wall to be in fluid communication. In some implementations, three or more of the interconnected walls meet at a joint. In these implementations, removing material from the dielectric is to form a passageway through the bond, the passageway being such that the passageway allows cells adjacent to the bond to be in fluid communication with each other. Including composing, forming.

In some implementations, the vapor cell is configured to detect target radiation. In such implementations, removing material from the dielectric includes forming a plurality of protrusions extending along the peripheral wall and into the open volume. In some variations, each of the plurality of protrusions has a largest dimension that is less than or equal to the wavelength of the target radiation. The target radiation may have a wavelength of at least 0.3 mm. However other wavelengths are possible. In some implementations, obtaining the dielectric includes removing material from the dielectric to form the first and second surfaces (eg, polishing, etching, machining, etc.).

In some implementations, the method includes disposing a steam or a source of steam within each of the plurality of cells prior to bonding. In these implementations, bonding the surfaces of the optical window includes entrapping a vapor or a source of vapor within each of the plurality of cavities.

In some implementations, removing material from the dielectric includes forming a hole through a peripheral wall of the dielectric to at least one of the plurality of cells. In such implementations, the method includes flowing steam through the holes and plugging the holes to seal the steam within the plurality of cells. In certain variations, the method may further include attaching a tube to the peripheral wall to extend the passageway defined by the hole. In these variations, closing the hole includes closing the end of the tube to seal the vapor within the plurality of cells.

In some implementations, the method includes forming a hole through the optical window. The hole is positioned to place at least one of the plurality of cells in fluid communication with the exterior of the optical window when the surface of the optical window is joined to the first surface of the dielectric. The method also includes flowing steam through the holes and plugging the holes to seal the steam within the plurality of cells. In certain variations, the method further includes attaching a tube to the optical window to extend the passage defined by the hole. In these variations, closing the hole includes closing the end of the tube to seal the vapor within the plurality of cells.

In some implementations, the optical window surface is a first window surface, and the optical window includes a second window surface opposite the first window surface. In such embodiments, the method includes removing material from the optical window to form a plurality of pockets extending partially from the second window surface to the first window surface. In a further implementation, the first window surface and the second window surface are bounded by a perimeter. Removing material from the optical window to form the plurality of pockets then includes forming the plurality of pockets in a sized configuration such that the effective dielectric constant of the optical window is determined. This effective dielectric constant is different from the inherent dielectric constant associated with the material forming the optical window.

In some cases, a method of manufacturing a vapor cell may be carried out according to the following examples. However, the examples are for illustrative purposes only. Any modifications in materials and methods may be made without departing from the scope of this disclosure.

(Example 1)
A double-sided p-type silicon wafer with orientation <100> was obtained. This silicon wafer had a diameter of 4 inches, a thickness of 500 μm, and a surface roughness R _a of 1 nm or less on all sides. The electrical properties of the silicon wafer included a resistance of 10 ⁴ Ω·cm. Glass wafers made of borosilicate glass were also obtained from Schott. The glass wafer was a MEMpax® wafer, 4 inches in diameter and 300 μm thick. The surface roughness was less than 0.5 nm.

Silicon and glass wafers were inspected in preparation for contact anodic bonding. Specifically, the wafers were visually inspected for chips, microcracks, and scratches. It was also verified that the wafer had a surface roughness of less than 1 nm. A 500 nm protective layer of SiO ₂ was grown on both sides of the silicon wafer using a wet growth process in an oxidation furnace. The temperature of the oxidation furnace was set at about 1100° C., and the processing time for silicon wafers was about 40 minutes. The thickness uniformity of the silicon wafer (with SiO ₂ layer) was verified to be within 500±6 nm over its 4 inch diameter area. It was also verified that the surface roughness was less than 1 nm.

The silicon wafer was formed into a silicon frame using either a Protolaser U4 microlaser tool or a Protolaser R microlaser tool to machine the silicon wafer material. The silicon frame included a perimeter wall and interconnected walls within the perimeter wall. Multiple cells of hexagonal shape were defined by interconnected walls. Notches were formed in the interconnected walls to define passageways between the multiple hexagonal shaped cells. The silicone frame was visually inspected with a loupe at 5× and 10× magnification for any cracks or chips that may have occurred during machining. If the silicon frame had zero or minimal surface defects, it was selected for subsequent vapor cell fabrication.

The silicone frame was then cleaned with methanol and isopropanol using a cotton swab and optical tissue. The silicon frame was then immersed in a buffered oxide etch (BOE) solution with a volume ratio of 10:1 and an etch rate of 55 nm/min at room temperature. The buffered oxide etch solution contained hydrofluoric acid buffered with ammonium fluoride. The silicon frame was soaked for at least 11 minutes to remove a 500 nm protective layer of SiO ₂ from the surface of each side of the silicon frame. After removal from the buffered oxide etch, the silicon frame was visually inspected. If embedded material from the machining process was found on the silicone frame, the silicone frame was discarded. If areas of SiO ₂ remained on the silicon frame, the silicon frame was again dipped into the buffered oxide etch solution, removed, and then re-examined. If the silicon frame did not have a 500 nm protective layer of SiO ₂ on either side, the silicon frame was selected to proceed to final cleaning and growth of a 100 nm SiO ₂ adhesion layer.

The silicone frame was cleaned with acetone and isopropanol using a cotton swab and optical tissue. An ultrasonic cleaner was used to assist the cleaning process by agitating the bath of acetone or isopropanol in which the silicone frame was immersed. A 100 nm layer of SiO ₂ was then grown on one side of the silicon frame. The temperature of the sample in the sputtering chamber was set at a minimum value of 600° C. to obtain a surface roughness of less than 1 nm for a 100 nm layer of SiO ₂ . The thickness uniformity of the 100 nm SiO ₂ layer was verified to be within 100±6 nm over the area of the silicon frame. If a silicone frame did not meet this uniformity criterion, it was discarded.

The silicon frame with a 100 nm SiO ₂ layer was then cleaned with methanol and isopropanol using a cotton swab and optical tissue to remove loosely adhered residues (such as those due to handling) on its surface. The silicone frame was then thoroughly cleaned with acetone and isopropanol using a cotton swab and optical tissue. A low power magnifying glass (e.g. 10x) was used during the thorough cleaning process for the first visual inspection, followed by a high power microscope (e.g. 50x-200x) for the second visual inspection. . If the silicone frame passed the second visual inspection, it was placed in a bath of acetone and ultrasonically cleaned at 40 kHz (eg, in a Branson Ultrasonic Cleaner CPX-952-117R). For example, the silicone frame may be placed in a glass beaker of acetone and ultrasonically cleaned for 20 minutes at room temperature. After ultrasonic cleaning, the silicone frames were dried with particle-free compressed air and stored in an airtight container until needed for bonding.

Separately, glass wafers were cleaned with methanol and isopropanol using cotton swabs and optical tissue. If necessary, the glass wafer was placed in a glass container of acetone and ultrasonically cleaned for 20 minutes at room temperature. After ultrasonic cleaning, the glass wafers were dried with particle-free compressed air and then stored in an airtight container until needed for bonding.

One silicon frame and one glass wafer were then placed into an assembly for anodic bonding. In the case of the silicon frame, the planar surface opposite the planar surface defined by the 100 nm layer of SiO ₂ was involved in the anodic bonding process. In this assembly, the planar surface of the silicon frame and the glass wafer were brought into contact to form a bonded surface, and this bonded surface was visually inspected to confirm the presence of optical fringes. The silicon frame was then heated to a temperature of approximately 400°C. After reaching this temperature, 600V was applied to the silicon and glass chips for approximately 15 minutes, thereby promoting the formation of the anodic bond. The bonded surface was inspected again to confirm the disappearance of the optical fringes indicating that the anodic bonding was complete. The anodic bond was then inspected for defects (eg, bubbles, microcracks, unbonded areas, etc.). If more than 80% of the area around the cell was defect-free, the anodic bond was further inspected for open channels (e.g., from a hole to the environment, from a hole to another hole, etc.). . If open channels were found, the anodic joint was not considered leak-free and the anodic joint was discarded.

Silicon and glass bodies joined by leak-free anodic bonding were cleaned in acetone and methanol. During this cleaning process, clean the unbonded surfaces of the silicone frame with acetone and methanol using a cotton swab and optical tissue to remove any residue (e.g. from the graphite plates of the assembly used to form the anodic bond). residue) was removed. The unbonded surface of the silicone frame was then visually inspected to ensure that there were no defects (eg, scratches, pitting, etc.) that could compromise the soon-to-form contact bond. The anode assemblies were then individually cleaned. Specifically, the anodic assemblies were placed alone (i.e., without other chips) in a glass beaker of acetone and ultrasonically cleaned for 20 minutes at room temperature. After ultrasonic cleaning, the anode assembly was dried with particle-free compressed air. A low power magnifying glass (eg, 10x) was used for the first visual inspection of the anodic assembly, followed by a high power microscope (eg, 50x to 200x) for the second visual inspection. A first and second visual inspection was utilized to ensure that no visible residue or deposits remained on the anodic assembly.

The anodic assembly - and the second glass wafer - were then placed into a clean room environment (eg, class 1000 or higher) to perform contact bonding. The planar surface defined by the 100 nm layer of SiO ₂ on the silicon frame of the anodic assembly and the planar surface of the second glass wafer were wiped with optical paper and acetone to remove macroscopic deposits from them. Object or foreign object removed. The pair was then immersed in an acetone bath (eg, a beaker containing acetone) and cleaned by ultrasonic cleaning for 15 minutes. The pair was then removed from the acetone bath, rinsed with isopropanol (eg, immersed in an isopropanol bath), and dried by blowing dry nitrogen gas.

The pair was then placed in a YES-CV200RFS plasma system and activated using nitrogen plasma for 45 seconds. In particular, a planar surface defined by a 100 nm layer of SiO ₂ on a silicon frame and a planar surface of a glass wafer were plasma activated. The RF power of the plasma system was set at approximately 75 W and the internal pressure was maintained at approximately 150 mTorr. Nitrogen gas was introduced into the plasma system at a volumetric flow rate of approximately 20 sccm. After activation by plasma cleaning, the pair was removed from the YES-CV200RFS plasma system and rinsed in deionized water for 5 minutes. This rinsing process served to hydroxylate the activated surface. In some variations, the rinsing process was performed using a basic aqueous solution (eg, an aqueous solution of ammonium hydroxide). Care was taken to prevent the two hydroxylated and activated surfaces from touching and coming together.

A paraffin-covered Cs tablet was then placed into the cavity, and both pieces were transferred into a vacuum chamber and mounted in a fixture with a "press finger." A fixture held the second glass wafer next to the silicon frame of the anodic assembly such that a gap was defined. The activated and hydroxylated surface of the glass wafer faced the activated and hydroxylated SiO ₂ surface of the silicon frame. The vacuum chamber was then sealed and pumped down to a low pressure (eg, less than 10 ⁻³ Torr).

Once the pressure in the vacuum chamber reaches its desired pressure, actuate the fixture to bring the activated and hydroxylated surface of the glass wafer into contact with the activated and hydroxylated _SiO surface of the silicon frame. Ta. A "pressing finger" was used to hold the contacted surfaces together for 20 minutes, thereby promoting the formation of a contact bond. In some variations, a "pressing finger" was used to apply target pressure (eg, about 2 MPa) continuously for 20 minutes. The bond was strengthened by annealing in an oven at approximately 90° C. for 8 hours. The annealing process released the Cs in the paraffin tablets.

(Example 2)
Howard Glass Co. , Inc. A thick glass wafer with a thickness of 1 mm and a diameter of 4 inches was obtained from. The surface roughness R _a of the thick glass wafer was 1 nm or less on both surfaces. Thin glass wafers made of borosilicate glass were also obtained from Schott. The thin glass wafer was a MEMpax® wafer, 4 inches in diameter and 300 μm thick. The surface roughness was less than 0.5 nm. Thick and thin glass wafers were tested in preparation for contact anodic bonding. Specifically, the glass wafers were visually inspected for chips, microcracks, and scratches. It was also verified that the wafer had a surface roughness of less than 1 nm.

A 100 μm Si wafer with a 500 nm layer of SiO ₂ on a single side was anodically bonded to a thick glass wafer with the SiO ₂ layer exposed on each side on the surface. A layer of Si was formed on a thick glass wafer with a 100 μm Si wafer. Alternatively, a layer of Si may be deposited on each side of the thick glass layer and _SiO2 may be sputtered onto the exposed surfaces. For example, a ~1 μm thick Si layer may be deposited using plasma enhanced chemical vapor deposition (PECVD) on both sides of a thick glass wafer, and a 500 nm protective layer of SiO ₂ on each side of the stacked frame. Sputtering may also be used.

Glass frames with Si and SiO _layers were then cut from the thick glass wafers using either a Protolaser U4 microlaser tool or a Protolaser R microlaser tool to machine the glass wafer material. The glass frame included a perimeter wall and interconnected walls within the perimeter wall. Multiple cells of hexagonal shape were defined by interconnected walls. Notches were formed in the interconnected walls to define passageways between the multiple hexagonal shaped cells. The glass frame was visually inspected with a loupe at 5x and 10x magnification for any cracks or chips that may have occurred during machining. If the glass frame had zero or minimal surface defects, that frame was selected for subsequent vapor cell fabrication.

The glass frame was then cleaned with methanol and isopropanol using a cotton swab and optical tissue. The glass frame with the Si and _SiO2 layers was then contacted (e.g., immersed in did). The buffered oxide etch solution contained hydrofluoric acid buffered with ammonium fluoride. The 500 nm protective layer of SiO ₂ was removed by keeping the surfaces in contact for at least 11 minutes, leaving Si on the glass frame. After removal from the buffered oxide etch, the glass frame was visually inspected. If embedded material from the machining process was found on the glass frame, the glass frame was discarded. If areas of SiO ₂ remained on the glass frame, the glass frame was again contacted with the buffered oxide etch solution, removed, and then re-examined. If the silicon frame did not have a 500 nm protective layer of SiO ₂ on its surface, the glass frame was selected to proceed to the final cleaning.

The glass frames were then cleaned with methanol and isopropanol using a cotton swab and optical tissue to remove loosely adhered residues (such as those due to handling) on their surfaces. The glass frame was then thoroughly cleaned with acetone and isopropanol using a cotton swab and optical tissue. A low power magnifying glass (eg, 10x) was used for the thorough cleaning process for the first visual inspection, followed by a high power microscope (eg, 50x-200x) for the second visual inspection. If the glass frame passed the second visual inspection, it was placed in a bath of acetone and ultrasonically cleaned at 40 kHz (eg, in a Branson Ultrasonic Cleaner CPX-952-117R). For example, the glass frame may be placed in a glass beaker of acetone and ultrasonically cleaned for 20 minutes at room temperature. After ultrasonic cleaning, the glass frames were dried with particle-free compressed air and stored in an airtight container until needed for bonding.

One glass wafer was selected and a 3 mm hole was cut using one of the Protolaser systems so that the hole could be aligned with one of the cells in the glass frame. The holes were used to fill the vapor cell with Cs using paraffin-coated Cs droplets.

Separately, thin glass wafers were cleaned with methanol and isopropanol using cotton swabs and optical tissue paper. If necessary, thin glass wafers were placed in a glass beaker of acetone and ultrasonically cleaned for 20 minutes at room temperature. After ultrasonic cleaning, the thin glass wafers were dried with particle-free compressed air and then stored in an airtight container until needed for bonding.

A glass frame (with a layer of Si) and one thin glass wafer were then placed into an assembly for anodic bonding. In the case of the glass frame, a planar surface defined by a layer of Si was involved in the anodic bonding process. In this assembly, the planar surface of the glass frame and the glass wafer were brought into contact to form a bonded surface, and this bonded surface was visually inspected to confirm the presence of optical fringes. The glass wafer was then heated to a temperature of approximately 400°C. After reaching this temperature, 600V was applied to the contacted glass bodies for approximately 15 minutes, thereby promoting the formation of the anodic bond. The bonded surface was inspected again to confirm the disappearance of the optical fringes indicating that the anodic bonding was complete. The anodic bond was then inspected for defects (eg, bubbles, microcracks, unbonded areas, etc.). If more than 80% of the area around the cell was defect-free, the anodic bond was further inspected for open channels (e.g., from a hole to the environment, from a hole to another hole, etc.). . If open channels were found, the anodic joint was not considered hermetic and the anodic joint was discarded. The same process was performed on each glass wafer and its corresponding surface on the glass frame.

The anodic bonded glass bodies were cleaned in acetone and methanol. During this cleaning process, the window with the 3 mm hole is cleaned with acetone and methanol using a cotton swab and optical tissue to remove any residue (e.g. from the assembly used to form the anodic bond). did. The window was then visually inspected to ensure that there were no defects (eg, scratches, pitting, etc.) that could compromise the contact bond that would soon form. The anode assembly was then washed separately. In particular, windows without fill holes were cleaned with acetone and methanol. A low power magnifying glass (eg, 10x) was used for the first visual inspection of the anodic assembly, followed by a high power microscope (eg, 50x to 200x) for the second visual inspection. A first and second visual inspection was utilized to ensure that no visible residue or deposits remained on the anodic assembly. A glass wafer measuring 5 mm square or larger was similarly cleaned and prepared to seal the fill hole using contact bonding.

The anodic assembly - and a square glass wafer with dimensions larger than 5 mm square - were then placed into a clean room environment (eg, class 1000 or higher) to perform contact bonding. For this pair, wipe the planar surfaces of the bonded structure with the filled holes and the planar surface of the glass wafer with optical paper and acetone to remove any macroscopic deposits or foreign matter from them. Ta. The pair was then removed from the acetone bath, rinsed with isopropanol, and dried by blowing dry nitrogen gas. This process was repeated until the surface was visibly clean using an optical loop.

The bonded structure and window were then placed in a YES-CV200RFS plasma system and activated using nitrogen plasma for 45 seconds. In particular, windows with filled holes and flat glass covers were activated by plasma. The RF power of the plasma was set at approximately 75 W, and the internal pressure was maintained at approximately 150 mTorr. Nitrogen gas was introduced into the plasma system at a volumetric flow rate of approximately 20 sccm. After plasma activation, the pair was removed from the YES-CV200RFS plasma system and rinsed in deionized water for 5 minutes. The bonded structure was carefully contacted with deionized water to avoid filling the cavities with water. This rinsing process served to hydroxylate the activated surface. In some variations, the rinsing process was performed using a basic aqueous solution (eg, an aqueous solution of ammonium hydroxide). Care was taken to prevent the two hydroxylated and activated surfaces from touching and coming together.

A paraffin-covered Cs tablet was then placed into the cavity using a 3 mm hole, and both pieces were transferred into a vacuum chamber and mounted in a fixture with a "pressing finger." A fixture held the glass piece next to the glass window of the anodic assembly such that a gap was defined. The activated and hydroxylated surface of the glass piece faced the activated and hydroxylated surface of the glass frame. The vacuum chamber was then sealed and pumped down to a low pressure (eg, less than 10 ⁻³ Torr).

Once the pair reached the desired pressure, the fixture was actuated to contact the activated and hydroxylated surface of the glass piece with the activated and hydroxylated surface of the anodic bonded structure. A "pressing finger" was used to hold the contacted surfaces together for 20 minutes, thereby promoting the formation of a contact bond. In some variations, a "pressing finger" was used to apply target pressure (eg, about 2 MPa) continuously for 20 minutes. The bond was strengthened by annealing at approximately 90° C. for 8 hours. The annealing process released Cs within the cavity.

In some aspects of what has been described, a method of manufacturing a vapor cell may be further described by the following examples.
(Example 1)
obtaining a dielectric having a first surface and a second surface opposite the first surface;
removing material from the dielectric to form a plurality of walls extending from the first surface to the second surface, the plurality of walls comprising:
a perimeter wall surrounding the open volume of the dielectric, and interconnected walls disposed within the open volume to partition the open volume into a plurality of cells, each cell defined by the first surface. forming a first opening defined by a first opening and a second opening defined by a second surface;
bonding a surface of the optical window to the first surface of the dielectric to form a seal around each of the first openings, the optical window forming a seal around each of the first openings of the plurality of cells; covering or joining the parts;
A method of manufacturing a steam cell, comprising:
(Example 2)
The method of Example 1, wherein removing material from the dielectric includes focusing a laser beam onto the dielectric to machine the material.
(Example 3)
The method of Example 1 or Example 2, wherein removing material from the dielectric comprises exposing the dielectric to a chemical to etch the material therefrom.
(Example 4)
Removing material from the dielectric forms a passageway through the at least one interconnected wall, the passageway providing fluid communication between cells separated by the at least one interconnected wall. The method of any one of Example 1 or Examples 2-3, comprising: configuring or forming.
(Example 5)
three or more of the interconnected walls are connected at a joint;
Removing material from the dielectric forms a passageway through the joint, the passageway being configured to allow cells adjacent the joint to be in fluid communication. including,
The method described in Example 1 or any one of Examples 2-4.
(Example 6)
The vapor cell is configured to detect target radiation;
Removing material from the dielectric includes forming a plurality of protrusions extending into the open volume along a peripheral wall, the plurality of protrusions having a maximum dimension less than or equal to a wavelength of the target radiation. ,including,
The method described in Example 1 or any one of Examples 2-5.
(Example 7)
7. The method of Example 6, wherein the target radiation has a wavelength of at least 0.3 mm.
(Example 8)
The method of Example 1 or any one of Examples 2-7, wherein obtaining the dielectric comprises removing material from the dielectric to form the first and second surfaces.
(Example 9)
disposing a steam or a source of steam within each of the plurality of cells prior to bonding;
Bonding the surfaces of the optical window includes entrapping a vapor or a source of vapor within each of the plurality of cavities;
A method as described in Example 1 or any one of Examples 2-8.
(Example 10)
Removing material from the dielectric includes forming a hole through a peripheral wall of the dielectric to at least one of the plurality of cells;
The method described in Example 1 or any one of Examples 2 to 9, comprising:
The method is
flowing steam through the hole;
occluding a hole to seal vapor within a plurality of cells.
(Example 11)
including installing a tube in the perimeter wall to extend the passageway defined by the hole;
Closing the hole includes closing the end of the tube to seal vapor within the plurality of cells;
Method as described in Example 10.
(Example 12)
forming a hole through the optical window, the hole connecting at least one of the plurality of cells to the exterior of the optical window when the surface of the optical window is joined to the first surface of the dielectric; forming, positioned in fluid communication with;
flowing steam through the hole;
plugging the holes to seal vapor within the plurality of cells;
The method of Example 1 or any one of Examples 2-9, comprising:
(Example 13)
including attaching a tube to the optical window to extend the passageway defined by the hole;
Closing the hole includes closing the end of the tube to seal vapor within the plurality of cells;
Method as described in Example 12.
(Example 14)
the surface of the optical window is a first window surface, and the optical window comprises a second window surface opposite the first window surface;
The method described in Example 1 or any one of Examples 2 to 13, comprising:
The method is
A method comprising removing material from an optical window to form a plurality of pockets extending partially from a second window surface to a first window surface.
(Example 15)
the first window surface and the second window surface are bounded by a periphery;
Removing material from the optical window to form multiple pockets
forming a plurality of pockets in a configuration of sizes such that the effective dielectric constant of the optical window is determined, the effective dielectric constant being different from the inherent dielectric constant associated with the material forming the optical window; , including forming;
Method as described in Example 14.
(Example 16)
the optical window is a first optical window;
The method described in Example 1 or any one of Examples 2 to 15, comprising:
The method is
disposing a steam or a source of steam within each of the plurality of cells;
bonding a surface of the second optical window to the second surface of the dielectric to form a seal around each of the second apertures, the second optical window being connected to the plurality of cells; forming a vapor or a source of vapor within each of the plurality of cells over a second opening of the cell.

In some aspects of what has been described, the vapor cell may be further described by the following examples.
(Example 1)
A dielectric material,
a first surface;
a second surface opposite the first surface; and a plurality of walls extending from the first surface to the second surface, the plurality of walls comprising:
a perimeter wall surrounding the open volume of the dielectric, and interconnected walls disposed within the open volume to partition the open volume into a plurality of cells, each cell defined by the first surface; an interconnected wall having a first opening defined by a first opening and a second opening defined by a second surface;
steam or a source of steam within each of the plurality of cells;
a first optical window having a surface covering the first opening and bonded to the first surface of the dielectric to form a seal around each of the first openings;
a second optical window having a surface covering the second opening and bonded to the second surface of the dielectric to form a seal around each of the second openings;
A steam cell comprising:
(Example 2)
The vapor cell is configured to detect target radiation;
the peripheral wall has a plurality of protrusions extending into the open volume, the plurality of protrusions having a maximum dimension that is less than or equal to a wavelength of the target radiation;
Vapor cell as described in Example 1.
(Example 3)
The vapor cell of Example 2, wherein the plurality of protrusions are evenly spaced along the peripheral wall.
(Example 4)
The vapor cell of Example 2 or Example 3, wherein each of the plurality of protrusions tapers into the open volume.
(Example 5)
A vapor cell according to Example 2 or any one of Examples 2-4, wherein the target radiation has a wavelength of at least 0.3 mm.
(Example 6)
One or both of the first optical window and the second optical window is
a first window surface opposite the second window surface, the first window surface being joined to the dielectric;
and a plurality of pockets extending partially from the second window surface to the first window surface.
(Example 7)
Examples 1 or 2-6, wherein one or both of the first optical window and the second optical window has an effective dielectric constant that is different from the intrinsic dielectric constant associated with the material forming the optical window. The steam cell according to any one of.
(Example 8)
One or both of the first optical window and the second optical window is
a first window surface opposite the second window surface, the first window surface being joined to the dielectric;
a plurality of pockets extending partially from the second window surface to the first window surface and configured with a size such that an effective dielectric constant of the optical window is determined; The vapor cell of Example 1 or any one of Examples 2-6, wherein the dielectric constant is different from the inherent dielectric constant associated with the material forming the optical window.
(Example 9)
9. The vapor cell of Example 8, wherein the plurality of pockets decrease in size along a direction parallel to the second window surface to define a decreasing effective dielectric constant.
(Example 10)
The vapor cell of Example 1 or any one of Examples 2-9, wherein the at least one interconnected wall comprises a passageway in fluid communication between cells separated by the at least one interconnected wall. .
(Example 11)
Embodiment 1 or any one of Examples 2-10, wherein three or more of the interconnected walls are connected at a joint, the joint comprising a passageway that provides fluid communication between the cells adjacent to the joint. Steam cell as described in.
(Example 12)
The vapor cell of Example 1 or any one of Examples 2-11, wherein the first optical window comprises a dielectric mirror.
(Example 13)
13. The vapor cell of Example 12, wherein the dielectric mirror is disposed along the surface of the first optical window that is bonded to the first surface of the dielectric.
(Example 14)
The vapor cell of Example 1 or any one of Examples 2-12, wherein the second optical window comprises an anti-reflection coating.

Although this specification contains many details, these are to be construed as descriptions of features specific to particular examples, rather than as limitations on the scope of claimed subject matter. Certain features that are described in this specification or illustrated in the drawings in the context of separate implementations may also be combined. Conversely, various features that are described or illustrated in the context of a single implementation can also be implemented in multiple embodiments separately or in any suitable subcombination.

Similarly, although the drawings depict operations in a particular order, this does not imply that such operations may be performed in the particular order shown or sequentially to achieve a desired result. It should not be understood as requiring that all operations shown be performed. Multitasking and parallel processing may be advantageous in certain situations. Furthermore, the separation of various system components in the implementations described above is not to be understood as requiring such separation in all implementations, and that the described program components and systems as a whole are It should be understood that the products can be integrated together in a single product or packaged into multiple products.

Several embodiments have been described. However, it will be appreciated that various modifications may be made. Accordingly, other embodiments are within the scope of the following claims.

Claims (30)

obtaining a dielectric having a first surface and a second surface opposite the first surface;
removing material from the dielectric to form a plurality of walls extending from the first surface to the second surface, the plurality of walls comprising:
a perimeter wall surrounding the open volume of the dielectric; and interconnected walls disposed within the open volume to partition the open volume into a plurality of cells, each interconnected wall comprising: connected to at least one other interconnected wall, each cell having a first opening defined by the first surface and a second opening defined by the second surface. to do and
bonding a surface of an optical window to the first surface of the dielectric to form a seal around each of the first openings, the optical window being connected to the plurality of cells; covering or joining the first opening of;
A method of manufacturing a steam cell, comprising: 2. The method of claim 1, wherein removing material from the dielectric includes focusing a laser beam onto the dielectric to machine the material. 2. The method of claim 1, wherein removing material from the dielectric includes exposing the dielectric to a chemical to etch material therefrom. Removing material from the dielectric forms a passageway through the at least one interconnected wall, the passageway forming a passageway in which cells separated by the at least one interconnected wall receive fluid. 2. The method of claim 1, comprising: configuring or forming to enable communication. three or more of the interconnected walls are connected at a joint;
Removing material from the dielectric forms a passageway through the junction, the passageway being configured to allow cells adjacent the junction to be in fluid communication. including forming, forming,
The method according to claim 1. the vapor cell is configured to detect target radiation;
Removing material from the dielectric forms a plurality of protrusions extending along the peripheral wall and into the open volume, the plurality of protrusions having a maximum dimension less than or equal to the wavelength of the target radiation. including having, forming,
The method according to claim 1 or any one of claims 2 to 5. 7. The method of claim 6, wherein the target radiation has a wavelength of at least 0.3 mm. A method according to claim 1 or any one of claims 2 to 5, wherein obtaining the dielectric comprises removing material from the dielectric to form the first and second surfaces. . disposing steam or a source of the steam within each of the plurality of cells prior to bonding;
bonding the surfaces of the optical window includes confining the vapor or the source of the vapor within each of a plurality of cavities;
The method according to claim 1 or any one of claims 2 to 5. Removing material from the dielectric includes forming a hole through the peripheral wall of the dielectric to at least one of the plurality of cells;
flowing steam through the hole;
6. A method according to claim 1 or any one of claims 2 to 5, comprising plugging the hole to seal the vapor within the plurality of cells. attaching a tube to the peripheral wall for extending a passageway defined by the hole;
Closing the hole includes closing an end of the tube to seal the vapor within the plurality of cells.
The method according to claim 10. forming a hole through the optical window, the hole forming a hole in at least one of the plurality of cells when the surface of the optical window is joined to the first surface of the dielectric; one positioned in fluid communication with the exterior of the optical window;
flowing steam through the hole;
closing the hole to seal the vapor within the plurality of cells;
The method according to claim 1 or any one of claims 2 to 5, comprising: attaching a tube to the optical window for extending a passage defined by the hole;
Closing the hole includes closing an end of the tube to seal the vapor within the plurality of cells.
13. The method according to claim 12. the surface of the optical window is a first window surface, the optical window comprising a second window surface opposite the first window surface;
A method,
Claim 1 or claims 2-5, comprising removing material from the optical window to form a plurality of pockets extending partially from the second window surface to the first window surface. The method according to any one of the above. the first window surface and the second window surface are bounded by a periphery;
Removing material from the optical window to form a plurality of pockets comprises:
The plurality of pockets are formed with a size such that an effective dielectric constant of the optical window is determined, and the effective dielectric constant is equal to a specific dielectric constant associated with a material forming the optical window. is different from, including, forming,
15. The method according to claim 14. the optical window is a first optical window;
The method according to claim 1 or any one of claims 2 to 5,
The method includes:
disposing steam or a source of the steam in each of the plurality of cells;
bonding a surface of a second optical window to the second surface of the dielectric to form a seal around each of the second openings; forming a cover over the second opening of the plurality of cells to confine the vapor or the source of the vapor within each of the plurality of cells. A dielectric material,
a first surface;
a second surface opposite the first surface; and a plurality of walls extending from the first surface to the second surface, the plurality of walls comprising:
a perimeter wall surrounding the open volume of the dielectric; and interconnected walls disposed within the open volume to partition the open volume into a plurality of cells, each interconnected wall comprising: interconnected walls connected to at least one other interconnected wall, each cell having a first opening defined by the first surface and a second opening defined by the second surface. a dielectric comprising a connected wall;
steam or a source of the steam within each of the plurality of cells;
a first optic having a surface covering the first opening and bonded to the first surface of the dielectric to form a seal around each of the first openings; window and
a second optic having a surface covering the second opening and bonded to the second surface of the dielectric to form a seal around each of the second openings; window and
A steam cell. the vapor cell is configured to detect target radiation;
the peripheral wall comprises a plurality of protrusions extending into the open volume, the plurality of protrusions having a maximum dimension that is less than or equal to a wavelength of the target radiation;
18. A vapor cell according to claim 17. 19. The vapor cell of claim 18, wherein the plurality of protrusions are evenly spaced along the peripheral wall. 19. The vapor cell of claim 18, wherein each of the plurality of protrusions tapers into the open volume. 19. The vapor cell of claim 18, wherein the target radiation has a wavelength of at least 0.3 mm. One or both of the first optical window and the second optical window,
a first window surface opposite a second window surface and bonded to the dielectric;
22. A vapor cell according to claim 17 or any one of claims 18 to 21, comprising a plurality of pockets extending partially from the second window surface to the first window surface. 17 or 17, wherein one or both of the first optical window and the second optical window has an effective dielectric constant different from an inherent dielectric constant associated with the material forming the optical window. 22. The steam cell according to any one of items 18 to 21. One or both of the first optical window and the second optical window,
a first window surface opposite a second window surface and bonded to the dielectric;
a plurality of pockets extending partially from the second window surface to the first window surface and configured with a size such that a certain effective dielectric constant of the optical window is determined; 22. A vapor cell according to claim 17 or any one of claims 18 to 21, wherein the effective dielectric constant is different from the inherent dielectric constant associated with the material forming the optical window. 25. The vapor cell of claim 24, wherein the plurality of pockets decrease in size along a direction parallel to the second window surface to define a decreasing effective dielectric constant. Steam according to claim 17 or any one of claims 18 to 21, wherein the at least one interconnected wall comprises a passageway in fluid communication between cells separated by the at least one interconnected wall. cell. 22. The method of claim 17 or claims 18 to 21, wherein three or more of the interconnected walls are connected at a joint, the joint comprising a passageway that brings cells adjacent to the joint into fluid communication. The steam cell according to any one of the items. A vapor cell according to claim 17 or any one of claims 18 to 21, wherein the first optical window comprises a dielectric mirror. 29. The vapor cell of claim 28, wherein the dielectric mirror is disposed along the surface of the first optical window bonded to the first surface of the dielectric. A vapor cell according to claim 17 or any one of claims 18 to 21, wherein the second optical window comprises an anti-reflection coating.

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